Influence of Nitrate Contamination on the Swell and Compressibility Characteristics of a Tropical Clayey Soil

This research work assessed the influence contaminated groundwater chemistry (especially nitrate contamination) on the volume change behavior during consolidation for a southwestern Nigerian clayey soil. 1-D Consolidation tests using deionized water and various concentrations of nitrate solution as the saturation/inundation liquid were performed on undisturbed clayey soil samples collected from Odi- Olowo Street (nitrate contamination prone area) in Akure, the capital of Ondo state, Nigeria. The compressibility/swell characteristics of the soil are influenced by nitrate contamination, as shown by the variation in the values of the coefficient of permeability, coefficient of consolidation, compression and swell indices (k, cv, Cc and Cs). This implies that the swell potential, magnitude and rate of settlement are affected. These properties directly influence the performance of shallow structural foundations. It was concluded that lack of chemical analysis for soil and groundwater in a nitrate contamination prone area before construction could lead to an overestimation of the swell and compressibility indices for the site. Permeability of the clayey soil increased significantly with increase in nitrate contamination, this portends the danger of emerging breakthrough of contaminants in the shallow contaminated zone through the underlying clayey layer to deeper confined aquifers being relied upon for portable drinking water

Soil Modification by the Application of Steel Slag

This paper provides experimental insights on the modification of a soil using electric arc furnace (EAF) steel slag, which is limitedly used as a construction material because of its volumetric instability. Various percentages of pulverized steel slag were applied to a soil, having poor engineering properties, with the aim of improving the engineering properties of the soil. Sieve analysis, consistency limits, specific gravity, compaction, California bearing ratio (CBR), unconfined compression and permeability tests were performed on the soil and each of the soil-slag mixtures. The plasticity and the uncured strength of the soil were reduced and increased, respectively, by the addition of an optimal steel slag content of 8%. Pulverized steel slag is therefore recommended as a low-cost modifier or stabilizer of lateritic soils with poor engineering properties, because it made the soil sample in this study better suited for use as a road pavement layer material

Effects Of Waste Engine Oil Contamination On The Plasticity, Strength And Permeability Of Lateritic Clay

This experimental investigation was carried out to determine the effects of contaminating a lateritic clay soil with waste engine oil on its geotechnical engineering properties. Varying percentages (0%, 2%, 4%, 6%, 8% and 10%) of waste engine oil were mixed with the soil, as a simulation of its contamination. Specific gravity, Atterberg limits, compaction, California bearing ratio (CBR) and permeability tests were conducted on the uncontaminated and contaminated soil samples. The specific gravity, plastic limit, optimum moisture content, maximum dry unit weight, and permeability of the soil decreased as its waste engine oil content increased. The liquid limit, plasticity index and CBR of the soil increased as its waste engine oil content increased. The plasticity and permeability properties of the soil make it unsuitable for use as a construction material, without modification or stabilization of the contaminated soil

Plasticity, Strength and Permeability of Reclaimed Asphalt Pavement and Lateritic Soil Blends

This paper presents the results of laboratory evaluation of the effects of the addition of reclaimed asphalt pavement (RAP), to an A-2 lateritic soil, on the plasticity, strength and permeability of the soil. The natural soil was classified as A-2-6(1), according to AASHTO classification system. RAP was added to the soil in 0, 4, 8 and 12%, by dry weight of the soil. Specific gravity, Atterberg limits, compaction, California bearing ratio (CBR), unconfined compression and permeability tests were conducted on each of the soil-RAP blends. Results obtained show that as RAP content in the blend increased, the plasticity index, optimum moisture content, maximum dry unit weight, swell potential, unconfined compressive strength and permeability decreased while the specific gravity, soaked and unsoaked California bearing ratios increased. These results indicate that RAP effectively improved, especially, the plasticity and permeability of the soil. It also indicates that deformation should be a major design criterion while planning the use of lateritic soil-RAP blend as a road pavement layer material

Residual Soils Derived from Charnockite and Migmatite as Road Pavement Layer Materials

Suitable soils for road pavement layer construction are getting depleted. Highway Engineers are consistently in search of locally-available and suitable soils for road construction. This paper investigates the potential use of residual soils derived from charnockite and migmatite as road pavement layer materials. Natural moisture content, sieve and hydrometer analyses, specific gravity, Atterberg limits, compaction, California bearing ratio (CBR), and permeability characteristics of soil samples collected from six different locations in Ekiti State, Nigeria were determined. The soils derived from charnockite have their average unsoaked CBR, soaked CBR and permeability to be higher than those of the soils derived from migmatite by 64.7%, 73.5% and 1750.9%, respectively. Consequently, some of the soils derived from charnockite satisfy the requirements by the Nigerian General Specification for use as subgrade and subbase materials, while those derived from migmatite generally have poor geotechnical properties. The soils derived from charnockite are recommended for use as pavement layer materials, while those derived from migmatite need to be stabilized before being used

Electrochemical influence of Aminobenzene on the pitting corrosion behaviour of Type 304 stainless steel in dilute sulphuric acid

The electrochemical influence of aminobenzene (AMB) concentrations on the pitting corrosion resistance of austenitic stainless steel type 304 in 3M sulphuric solutions with 3.5% sodium chloride addition was evaluated through potentiodynamicpolarization technique. The pitting potential, passivation potential, passivation range, nucleation resistance and passivation capacity were analyzed with respect to specific aminobenzene concentrations. Under impressed potential difference the stainless steels in acid solution acquired a passive state, with breakdown at the transpassive region (pitting potential), however this was greatly increased to higher values with aminobenzene additioncausing significant increase in the passivation range and potentials greatly higher than the value that necessitates pitting in the acid media due to enhanced corrosion resistance of the stainless steel through formation of protective film of aminobenzene molecules. The results obtained establish the dynamic relationship and interaction between the aminobenzenecation concentration and electrochemical parameters in the corrosion behavior of the stainless steel at ambient temperature of 25 oC

Effect of corncob ash on the geotechnical properties of lateritic soil stabilized with Portland cement

Portland cement has been effectively used to improve the engineering properties of some local soils for construction of stabilized pavement layers, stabilized earth buildings and support layer for the foundation of buildings. However, cement is expensive and its use is unsustainable, necessitating the search for alternative materials for its total or partial replacement. This paper aims at providing experimental insights on the engineering properties of lateritic soil stabilized with cement-corncob ash (CCA) to ascertain its suitability for use as a pavement layer material. Series of specific gravity, consistency limits, compaction, California bearing ratio (CBR) and permeability tests, considering three CCA blends and four CCA contents, varying from 0 to 12%, were carried out. The results show that the addition of CCA to the soil generally reduced its plasticity, swell potential and permeability; and increased its strength. CCA-stabilization, aside being more economical and environment-friendly than cement-stabilization, improved the geotechnical properties of the soil for pavement layer material application

REMOVAL OF LEAD, CADMIUM AND NICKEL BY SAWDUST-MODIFIED TROPICAL CLAY FOR USE AS LANDFILL LINER MATERIAL

Access to groundwater, a major source of direct drinking water in many developing countries, should not be assumed as access to safe drinking water. There is a need to prevent or minimize the contamination of groundwater, especially arising from solid waste disposal. This research work investigated the suitability of using clay and bentonite modified with sawdust as landfill liner materials for minimizing the migration of Pb2+, Cd2+ and Ni2+ in order to protect the environment and public health. Series of laboratory tests were carried out to determine the chemical and mineralogical composition, microstructural analysis of the clay and bentonite in order to characterize the samples. The effects of adding varying percentages of sawdust to the clay and bentonite on their geotechnical properties were determined. The removal of each of Pb2+, Cd2+ and Ni2+ by the clay, bentonite, sawdustmodified-clay and sawdust-modified-bentonite was investigated using the batch equilibrium adsorption technique for varying initial metal ion concentrations and contact times, while the pH, adsorbent dosage and temperature were kept constant. Results obtained show that the application of up to 8% sawdust to the clay satisfies standard geotechnical properties requirements for use as clay landfill liner, whereas the bentonite and its modification with sawdust did not. Each of the sawdust-modified-clay and sawdust-modified-bentonite removed more Pb2+, Cd2+ and Ni2+ than the clay and bentonite without sawdust, respectively. The Dubinin-Radushkevich model was found to be the best adsorption isotherm that described the Pb2+, Cd2+ and Ni2+ adsorption by the sawdust-modified-clay, while the pseudo-second-order kinetic model best described the rate of adsorption of these metal ions by the sawdust-modified-clay. The adsorption by the modified clay can be described as physical adsorption due to weak van der Waals forces. The order of removal of the metals by the clay and sawdust-modified-clay followed a trend of Pb2+ > Cd2+ > Ni2+, while that of bentonite and sawdust-modified-bentonite followed a trend of Pb2+ > Ni2+ > Cd2+. The clay and sawdust-modified-clay removed Pb2+ and Cd2+ better than the bentonite and sawdustmodified-bentonite, respectively, while the bentonite removed Ni2+ better than the clay. Clay modified with sawdust was found suitable and recommended for use as a landfill liner material in a composite lining system, thereby providing a low-cost and sustainable approach to improving the capacity of the clay to minimize the migration of Pb2+, Cd2+ and Ni2+ from landfills, and protecting the environment (particularly groundwater resources) and public health

Compressive Strength Development for Cement, Lime and Termite-hill Stabilised Lateritic Bricks

This study evaluated the compressive strength of lateritic bricks stabilised with cement, lime and termite-hill, moulded with CINVA-Ram. The engineering characteristics and classification of the lateritic soil sample were determined, also the characteristic compressive strength of stabilised bricks as well as the unstabilised bricks were investigated after 7, 14 and 28 days of curing. The total number of bricks moulded was ninety and they were 290 mm x 140 mm x 90 mm in size. Each of the three stabilisers were added in varying proportions of 8%, 10% and 12% by weight of the lateritic soil for producing the bricks. Compressive strength test conducted after 28 days curing revealed that the cement stabilised bricks developed a rapid increase in strength than the lime stabilised and termite-hill stablised bricks. In all, the compressive strength increased with increasing proportion of the stabilisers. However, the unstabilised bricks developed strength which was more than the 10% termite-hill stabilised bricks after 28 days. It was deduced that cement stabilization is adequate where early strength is targeted on the field

Effects of Curing Condition and Curing Period on the Compressive Strength Development of Plain Concrete

This paper presents the results of an experimental study on the effects of curing methods and curing ages on the compressive strength development of ordinary Portland cement concrete in a tropical environment. Fifteen (15) concrete cubes each were cured by immersion in potable water, immersion in lime water, covering with wet rug, covering with plastic sheets and air-drying. For each of these curing methods, the average compressive strength of concrete cubes was determined after 3, 7, 14, 28 and 90 days curing periods. The results obtained discourages the use of curing by air-drying method and also suggests limiting the use of the other curing methods to 28-days period. Generally, the highest compressive strength was obtained for concrete cured by immersion in lime water